Poster Presentation 35th Lorne Cancer Conference 2023

CAMK2 represents an ‘actionable’ target downstream of the oncogenic pseudokinase PEAK1 in triple negative breast cancer (#361)

Xue Yang 1 2 , Xiuquan Ma 1 2 , Kimberley C Clark 1 2 , David R Croucher 3 4 , Elizabeth V Nguyen 1 2 , Sung-Young Shin 1 2 , Lan K Nguyen 1 2 , Terry C C Lim 1 2 , Roger J Daly 1 2
  1. Cancer Program, Monash Biomedicine Discovery Institute, Clayton, VIC, Australia
  2. Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, Australia
  3. Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
  4. St Vincent's Clinical School, Faculty of Medicine, The University of New South Wales, Darlinghurst, NSW, Australia

The PEAK family of pseudokinases, comprising PEAK1-3, are oncogenic scaffolding proteins that undergo homo- and heterotypic association to assemble protein complexes with contrasting signal outputs.  PEAK1 is implicated in several poor prognosis human cancers, including triple negative breast cancer (TNBC), but therapeutic targeting of this pseudokinase is challenging due to its lack of catalytic activity. To address this, we undertook a proteomics screen, identifying calmodulin-dependent protein kinase 2 (CAMK2) D and CAMK2G as interactors for PEAK1/2 homo- and heterotypic complexes. PEAK1 promoted CAMK2D/G activation in TNBC cells in a manner dependent on CAMK2 association with the PEAK1 N-terminus and a novel PEAK1/PLCg1/Ca2+ signalling pathway. PEAK1 signalling via CAMK2D/G was required for efficient migration and invasion of TNBC cells and regulated tyrosine phosphorylation of p130Cas, a key component of focal adhesions. To achieve pharmacologic targeting of PEAK1/CAMK2 signalling, we repurposed RA306, a second generation CAMK2 inhibitor under pre-clinical development for treatment of cardiovascular disease. RA306 demonstrated on-target activity against CAMK2 in TNBC cells and inhibited PEAK1-enhanced migration and invasion in vitro. Moreover, RA306 significantly attenuated TNBC xenograft growth and blocked metastasis in a manner mirrored by CRISPR-mediated PEAK1 ablation. Overall, these studies reveal a novel link between pseudokinase and intracellular Ca2+ signalling and identify CAMK2 as an ‘actionable’ target downstream of the oncogenic scaffold PEAK1.